Some Windows machines boot up in BitLocker recovery mode since a recent security update. Microsoft is aware of it and is warning users.
The culprit is the July 2024 Windows security update, KB5040442. Because this activates BitLocker’s protection mechanism for some users, they need to enter the unique recovery key. This is sometimes easier said than done, such as when BitLocker keys proved necessary in the global CrowdStrike outage. The key is retrievable by logging into the linked Microsoft account. BitLocker ensures that data on a device is protected and encrypted so that malicious parties cannot pull it from the drive when a Windows system is no longer in use or is stolen.
Tip: Culprit behind global Windows outage revealed
Substantial changes
Normally, a BitLocker recovery screen activates as soon as a system experiences substantial changes. However, a monthly security update is not supposed to trigger this. BitLocker is supposed to activate when the hardware gets swapped around, new firmware is installed, or the Trusted Platform Module (TPM 2.0) is changed.
The security update impacts all Windows 10 and 11 versions and Windows Server 2008 through 2022.
Update issues
It is fairly common for Windows updates to encounter similar problems. Last November’s KB5031455, for example, caused a flood of error messages, while it hit again a month later. Then, Windows 11 23H2 was found to lead to performance degradation. It could also be worse, as when KB5029351 caused a Blue Screen of Death for some users.
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